Control apparatus for well tool anchor



Feb. 28, 1967 o. E. YOUNG 3,306,360

CONTROL APPARATUS FOR WELL TOOL ANCHOR Filed Aug. 9, 1965 4 Sheets-Sheet 1 flay/0 you/7y INVENTOR.

gWM/WM ATTOR/Vf) Feb. 28, 1967 D. E. YOUNG CONTROL APPARATUS FOR WELL TOOL ANCHOR Filed Aug. 9, 1965 4 Sheets-Sheet 2 mxem INVENTOR.

ATTORNEY Feb. 28, 1967 0. E. YOUNG 3,306,360

CONTROL APPARATUS FOR WELL TOOL ANCHOR Filed Aug. 9, 1965 4 Sheets-Sheet a ATTORNEY Feb. 28, 1967 D. E. YOUNG 3,306,360

CONTROL APPARATUS FOR WELL TOOL ANCHOR Filed Aug. 9, 1965 4 Sheets-$heet 4 flay/o 5. Young INVENTOR.

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United States Patent M 3,306,360 CONTROL APPARATUS FOR WELL TOOL ANCHOR David E. Young, Bellaire, Tex., assiguor to Schlumberger Tfecrhnology Corporation, Houston, Tex., a corporation 0 exas Filed Aug. 9, 1965, Ser. No. 482,020 16 Claims. (Cl. 166120) This is a continuation-in-part of application Serial No. 374,534, filed June 11, 1964, now abandoned.

This invention relates to apparatus adapted for operation in a well bore; and, more particularly, to control apparatus for a hydraulically actuated anchor for well tools, which anchor, when set in place, will hold the tool fixed against well pressures acting from either direction by anchoring force proportionately related to the acting pressure.

In conducting such well-completion operations as acidizing, cementing, or fracturing, a full-opening well packer dependently coupled from a tubing string is positioned at a particular depth in a cased well and the packer set to isolate the formation interval to be treated from the remainder of the well bore thereabove. Treating fluids are then pumped downwardly at high pressure through the tubing and packer and introduced into the fonnation being treated through perforations appropriately located in the casing. In those instances where a well having several producing formations is being completed, a selectively operable bridge plug can be dependently coupled beneath the full-opening packer. Such a bridge plug per mits packing-off zones of selected length in the well bore for selective treatment of different formation intervals with only a single trip into the well.

It will be appreciated that such packers and bridge plugs must be capable of withstanding high pressures acting from either direction. Furthermore, during the course of typical completion operations, a packer and bridge plug are usually subjected to high pressures acting alternately from both above and below them. Thus, it is necessary to securely anchor them against movement in either longitudinal direction.

Accordingly, it is an object of the present invention to provide new and improved apparatus for controlling hydraulically actuated wall-engaging anchoring means for well tools, which means are pressed into anchoring engagement with a force proportionately related to the pressure of the well fluid.

A bridge plug employing the control apparatus of the present invention includes selectively operable wall-engaging means including a hydraulic system which, in response to the pressure of well fluids, is arranged to be pressed into anchoring engagement with a force proportionately related to this fluid pressure. After the packing means and anchor means are selectively engaged, the new and improved control apparatus for the hydraulic system responds to the pressure differential of the well fluids across the packing means to maintain the anchor against the casing with an anchoring force which is proportionately related to this pressure differential.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a view of a full-bore packer and a bridge plug including the control apparatus of the present invention and depicted as they would appear within a well bore;

3,306,360 Patented Feb. 28, 1967 FIGS. 2A-2C are successive, detailed cross-sectional views of an embodiment of a bridge plug having the control apparatus of the present invention;

FIG. 3 is an isometric view showing particular details of a locking groove employed with the bridge plug of FIG. 2;

LF-IG. 4 is a cross-sectional View taken along the line 4-4 of FIG. 2B;

FIGS. 5A and 5B are detailed, successive cross-sectional views of another embodiment of a bridge plug with the control apparatus of the present invention; and

FIG. 6 is a view showing particular details of a valve employed with the bridge plug of FIG. 5.

As seen in FIG. 1, a typical full-bore packer 10 is dependently connected to a tubing string 11 and positioned within a well bore 12 having a casing 13 set therein. A retrievable bridge plug 14 is shown sealingly and anchoringly engaged with the casing 13. An overshot 15 dependently connected beneath the well packer 10 is releasably coupled to a fishing neck 16 on the bridge plug 14. This releasable coupling allows the bridge plug 14 to be set at the lower limit of a particular formation interval and the packer 10 subsequently set at any point thereabove irrespective of the length of the tubing sub 17 connecting the packer to the bridge plug.

Turning now to FIGS. 2A-2C, the retrievable bridge plug 14 depicted in FIG. 1 includes a rotatable tubular sleeve member 18 (FIG. 2A) having one end telescopically arranged within and thre-adedly engaged with a tubular housing member 19 (FIGS. 2B2C). Elastomeric packing means 20 (FIG. 28) mounted around the tubular sleeve 18 are arranged to be foreshortened and expanded outwardly into sealing engagement whenever the tubular sleeve is rotated in one direction relative to the housing 19. Rotation of the tubular sleeve 18 in the opposite direction will, of course, allow the elastomeric packing means 20 to relax and return to its normal position.

An actuating body member or index mandrel 21 (FIGS. 2A-2C) is slidably engaged and co-rotatively secured within the tubular sleeve 18 and extended on into the housing 19. Normally engaged latch means 22 FJG. 2B) releasably latch the mandrel to the housing 19 to prevent the mandrel 21 from shifting longitudinally until the mandrel has first been rotated a predetermined amount as it screws the tubular sleeve 18 inwardly into the housing to foreshorten the packing means 20.

The housing 19 is initially restrained against rotation by a set of conventional spring-biased drag blocks 23 (FIG. 2C) mounted around a portion of the housing and arranged to be continuously biased outwardly against the casing wall. As is customary, the force exerted by these blocks is not sufficient to prevent the bridge plug 14 from being longitudinally shifted or traversed within the casing. Once the bridge plug 14 has been brought to rest, however, the static frictional drag imposed by the drag blocks 23 will be sufficient to eifective-ly hold the housing 19 relatively fixed against movement of the index mandrel 21.

A hydraulically actuated radially expansible friction anchor 24 (FIGS. 2B2C) mounted on the housing 19 is adapted to be pressed against the casing whenever the mandrel 21 shifts longitudinally in either direction with respect to the housing to anchor the bridge plug 14 relative to the casing.

The lower end of the rotatable tubular sleeve member 18 is threadedly engaged and received within particularly arranged righthand threads 25 (FIG. 2B) around the upper end 26 of the housing 19. The sleeve member 18 0 is provided with a series of longitudinal, inwardly projecting splines 27 spaced around its inner bore 28. These splines 27 are cooperatively and slidably received within a series of substantially elongated, complementary, longitudinal spline grooves 29 formed around the periphery of the index mandrel 21. As will be subsequently described, once the latch means 22 has released the mandrel, these splines 27 and their longer mating grooves 29 allow the mandrel 21 to freely shift longitudinally with respect to the sleeve member 18 but prevent these members 18, 21 from rotating relative to one another.

The elastomeric packing means are mounted around the tubular sleeve 18 and disposed between the upper end 26 of the housing and a downwardly facing annular shoulder 30 provided around the sleeve. A tubular guard 31 loosely disposed around the tubular sleeve 18 and inside of the packing means 20 allows the sleeve to rotate freely Within the packing means. Thus, as the tubular sleeve 18 is being screwed downwardly into the housing 19 to foreshorten the packing means 20, no torque is applied against the internal circumferential surfaces of the packing means. For similar reasons, a freely swiveling annular ring 32 around the upper end of the packing means 20 allows the sleeve .18 to rotate without twisting the upper end of the packing means.

The releasable latching means 22 normally holds the index mandrel 21 fixed longitudinally with respect to the housing 19, but is so arranged that it is selectively released by torquing the mandrel in a clockwise direction as the packing means 20 are being foreshortened. The latching means 22 is comprised of a reciprocable lug member 33 which is slidably received within an inwardly directed lateral bore or recess 34 provided in a central portion of the housing 19. A spring member 35 biases the lug 33 inwardly so that its inner end 36 is engaged within a T- shaped groove 37 in the periphery of the mandrel 21 whenever this groove is in juxtaposition with the end of the lug.

As shown in detail in FIG. 3, the flat-bottomed T- shaped groove 37 has an elongated portion 38 extending longitudinally along the mandrel 21 and a branch portion 39 extending to the right and perpendicularly away from the center of the longitudinal groove portion 38. The branch portion 39 diverges as it extends away from the elongated groove portion 38 with the flat bottom 40 being terminated and slightly rounded-off where it intersects and merges into the outer surface of the mandrel 21.

It will be understood that so long as the inner end 36 of the spring-loaded lug 33 is within the longitudinal groove portion 38, the mandrel 21 can shift only a very limited distance longitudinally. Left-hand rotation of the index mandrel 21 relative to the housing 19 is of course prevented by the end 36 of the lug 33 engaging the straight shoulder 41 of the longitudinal slot portion 38. Moreover, as the bridge plug 14 is being raised or lowered within the casing, it will be appreciated that the lug end 36 will respectively shifted into the positions 42 and 43 shown by dashed lines in FIG. 3. Thus, so long as there is either an upward or downward force on the mandrel 21, shoulder 44 or shoulder 45 will prevent the mandrel from being rotated to the right as well. The mandrel 21, therefore, must first be shifted in such a manner that the lug end 36 is substantially in a neutral position 46 before it can be torqued to the right for setting of the bridge plug 14. Once the spring-loaded lug 33 is disengaged from the T-groove 37, the index mandrel 21 is of course free to shift longitudinally relative to the housing 19 as well as to the sleeve member 18.

Mounted around the housing 19 is an expansible anchor 24 (FIGS. 2B2C) with parts thereof being shown in detail in FIG. 4. This anchor 24 includes an elastomeric sleeve 47 encircling the housing 19 with a plurality of elongated casing-contacting members 48 and 49 being mounted uniformly around the periphery of this sleeve. The elarged upper 50 and low 51 ends of the elastomeric sleeve 47 are sealing secured within opposed annular recesses 52 and 53 provided in the housing 19 to provide a fluid-tight space 54 between the sleeve and housing.

Each of the casing-engaging members 48 and 49 are elongated and have a thick, arcuate, cross-section (FIG. 4). Alternate ones 48 of these casing-engaging members are centrally aligned and mounted along the outer convex surface of relatively thin, elongated, arcuate backing members 55. A sufficient number of these mounted members 48 are disposed uniformly around the periphery of the elastomeric sleeve 47 so that the backing members 55 substantially encompass the sleeve. The remaining unmounted casing-engaging members 49 are alternately disposed between the mounted casing-engaging members 48 in such a manner that the unmounted members 49 will straddle adjacent backing members 55 and cover the gap 56 therebetween.

The ends of the casing-engaging members 48 and 49 are disposed within the opposed annular recesses 52 and 53 around the housing 19 at opposite ends of the members (FIGS. 2B2C). Arcuate leaf springs 57 extending from the housing recesses 52 and 53 are engaged with the opposite ends of the members 48 and 49 to normally bias the casing-engaging members radially inwardly.

Turning now to the hydraulic system controlled by the apparatus of the present invention, the housing 19 is formed in such a manner as to provide an annular chamber 58 (FIG. 2B) above the upper end of the anchor 24. A similar annular chamber 59 (FIG 2C) is also formed below the lower end of the anchor 24. An annular clearance space 60 between the index mandrel 21 and housing 19 provides fluid communication from the upper chamber 58 to the lower chamber 59. A plurality of radial ports 61 through the housing 19 adjacent the elastomeric sleeve 47 provide fluid communication from this clearance space 60 into the sealed space 54- underneath the elastomeric sleeve.

The upper end of the upper annular chamber 58 and the lower end of the lower annular chamber 59 are respectively closed by annular piston members 62 and 63 which are slidably mounted relative to both the housing 19 and the index mandrel 21. The upper slidable piston member 62 (FIG. 2B) is biased upwardly by a spring 64 which normally urges this piston member against a downwardly directed shoulder 65 formed in the housing 19 at the upper end of the upper chamber 58. Annular grooves around the outer and inner surfaces, respectively, of the upper piston member receive O-rings 66 and 67 which fluidly seal the slidable piston member 62 relative to the housing 19 as well as to the index mandrel 21.

In a similar manner, the lower slidable piston member 63 (FIG. 2C) is biased downwardly by a spring 68 so that the lower piston member normally rests against an upwardly directed shoulder 69 formed in the housing 19 at the lower end of the lower chamber 59. Similarly, external and internal annular grooves around the iston member 63 receive O-rings 70 and 71 to fluidly seal the slidable piston member relative to both the housing 19 and the index mandrel 21.

A shoulder 72 (FIG. 2B) located on the mandrel 21 a short distance above the upper slidable piston 62 is so arranged that whenever the mandrel 21 shifts downwardly, the shoulder will engage the upper piston '62 and force it downwardly. Similarly, a second shoulder 73 (FIG. 2C) is provided on the mandrel to engage and shift the lower piston member 63 upwardly whenever the mandrel 21 shifts in that direction.

It will be appreciated that with a suitable fluid in the above-described hydraulic system, longitudinal shifting of the mandrel 21 in either direction will expand the elastomeric sleeve 47 of the anchor 24 and press the casingengaging members 48 and 49 against the casing. Thus, as the tubular sleeve 18 (FIG. 2B) is being rotated downwardly by the mandrel 21 to set the packing means 20, the upper piston 62 (FIG. 2B) will be engaged and forced downwardly by the mandrel shoulder 72. Downward shifting of this piston '62 will, of course, cause the anchor 24 to be extended into anchoring engagement with the casing.

Turning now to the control apparatus of the present invention, a compensating chamber 74 (FIG. 2C) in the housing 19 beneath the lower piston member 63 maintains a supply of fluid in the hydraulic system as well as compensates for thermal expansion of the fluid. The lower end of this compensating chamber 74 is closed by a slidable annular compensating piston member 75 having O-rings 76, 77 around its outer and inner surfaces which fluidly seal the compensating piston relative to the housing 19 and mandrel 21. A relatively light spring 78 underneath the compensating piston holds it oflf of an annular spacer member 79 which, in turn, rests on an upwardly facing housing shoulder 80. The spring 78 will contract and expand in accordance with thermal expansion of the hydraulic fluid as well as continuously bias the compensating piston 75 against the hydraulic fluid.

Selectively controlled fluid communication is provided between the compensating chamber 74 and the remainder of the hydraulic system through an annular clearance space formed by a reduced-diameter portion 81 around the index mandrel 21. This reduced-diameter portion 81 is arranged to be in juxtaposition with the lower piston 63 whenever the mandrel 21 is shifted only a slight distance longitudinally however, the inner sealing member 71 around the inner bore of lower piston member 63 fluidly seals the piston to the mandrel at either 82 or 83, depending upon the direction in which the mandrel shifts.

Turning now to the operation of the bridge plug 14, whenever the bridge plug has been positioned at the depth in the well bore where it is desired to set the packing means 20, the tubing string 11 is manipulated properly to shift the lug end 3-6 to its neutral position 46. The tubing 11 and index mandrel 21 are then rotated to the right to cam the locking lug 33 (FIG. 2B) back into its recess 34 and free the mandrel from the housing 19. The housing 19 is of course secured by the drag blocks 23. Accordingly, right-hand rotation of the mandrel 21 frees it from the housing 19 and allows it to be picked up as it simultaneously (in view of splines 27 and grooves 29) begins to screw the sleeve 18 downwardly into the housing along the threads 25.

As the sleeve 18 is screwed downwardly, it will be appreciated that the downwardly facing shoulder 30 around the upper end of the sleeve advances toward the upper end 26 of the housing 19 to foreshorten the packing means 20. The pitch of the threads 25 is appropriately selected so that approximately only three-quarters of a revolution is required to advance the sleeve 18 a sufiicient distance to fully displace the packing means 20 into sealing engagement with the casing. An upwardly directed housing shoulder 84 is arranged to be engaged by the lower end 85 of the sleeve 18 and halt further advancement of the sleeve whenever it has rotated approximately three-quarters of a revolution which otherwise might allow the lug end 36 to re-enter the T-shaped groove 37 and relatch the mandrel 21.

It will be further appreciated that when the mandrel 21 has been freed and is moved upwardly only a slight distance with respect to the housing 19, the reduceddiameter portion 81 (FIG. 2C) of the mandrel is shifted out of juxtaposition with the lower slidable piston member 63. When this reduced-diameter portion 81 shifts a slight distance upwardly relative to the lower slidable piston member 63, O-ring 71 sealingly engages the periphery of the mandrel at 83 to trap all hydraulic fluid in the system above the lower slidable piston member. It will also be noted that continued upward travel of the mandrel 21 will soon bring the lower mandrel shoulder 73 into engagement with the lower piston member 63 and begin to shift it upwardly. Thus, with the upper piston 62 engaged against shoulder 65 and sealed by O-rings 66 and 67, as the shoulder 73 continues to advance the lower slidable piston member 63 upwardly in the housing 19 toward the upper piston 62, a hydraulic pressure is developed in the system. This developed hydraulic pressure expands the elastomeric sleeve 47 and extends the casing-engaging members 48, 49 (FIGS. 2B2C) of the anchor 24 outwardly into tight engagement with the well casing. It will be understood, of course, that due to the relative incompressibility of hydraulic fluids, a considerable hydraulic pressure will be developed within the hydraulic system; and, moreover, that this pressure will "be imposed against the substantial surface area of the elastomeric sleeve member 47. Thus, the casing-engaging members 48 and 49 will be pressed against the casing with a considerable force, which force will be suflicient to anchor the bridge plug 14 against substantial longitudinal directed forces.

It will be appreciated, therefore, that after the bridge plug is set and the mandrel 21 released, should the pressure in the well bore below the bridge plug 14 be greater than the pressure below, the pressure differential will act on the eflective cross-sectional area of the index mandrel 21 and shift the mandrel further upwardly. Upward shifting of the mandrel 21 accordingly drives the lower slidable piston member 63 further upwardly, which action will, of course, further increase the hydraulic pressure within the system to press the casing-engaging members 48 and 49 of the anchor 24 even more tightly against the well casing.

Should, perchance, the pressure in the well bore above the bridge plug 14 become greater than that therebelow, the mandrel 21 will similarly be shifted downwardly. As the mandrel 21 shifts downwardly, the lower slidable piston member 63 will, of course, be returned to its initial position against shoulder 69 by spring 68 and the hydraulic pressure will be momentarily reduced. As the mandrel 21 continues to travel downwardly, however, the lower slidable piston member 63 is quickly resealed by O-ring 71 around the mandrel 21, but now at 82 on the opposite side of reduced-diameter portion 81. The upper mandrel shoulder 72 will then engage the upper slidable piston member 62 and begin shifting it downwardly against spring 64. This downward movement will, of course, again increase the hydraulic pressure within the fluid-filled system to maintain the casingengaging members 48 and 49 tightly pressed against the well casing.

Accordingly, it will be appreciated that well pressure acting on the bridge plug 14 from either longitudinal direction will proportionately increase the hydraulic pressure which correspondingly forces the casing-engaging members 48, 49 even more tightly against the well casing. Furthermore, the bridge plug 14 will remain anchoringly engaged so long as the pressure seals in the hydraulic system remain effective.

It should be noted that once latching means 22 releases, the mandrel 21 is relatively free to shift longitudinally in either direction with respect to the tubular sleeve member 18 in view of the diflerence in lengths of the splines 27 and the spline grooves 29. Thus, the mandrel 21 can shift upwardly a considerable distance within the tubular sleeve 18 Without imposing an upward force against the sleeve which might otherwise tend to rotate the sleeve upwardly along threads 25.

As seen in FIGS. 2A-2C, the mandrel 21 is provided with a central axial bore 86 which is selectively opened and closed by an equalizing valve 87. Thus, whenever the bridge plug 14 is being traversed through a fluidfilled well bore, the equalizing valve 87 is left open to allow part of the fluids in the well to be bypassed through the mandrel bore 86 rather than all of the fluids being forced through the confined annular space between the casing and retracted packing means 20. A junk pusher 88 (FIG. 2C) at the lower end of the housing 19 has 7 ports 89 therein which allow fluids to enter the central bore 86 of the index mandrel 21.

The upper end of the mandrel 21 is capped by the conventional fishing neck 16 arranged to cooperatively receive the tubular overshot 15 which may be dependently coupled beneath a full-bore packer 10 with a hold-down (not shown) or to a tubing string 11. Matched J-slots 90 (FIG. 2A) are provided on opposite sides of the fishing neck 16 for receiving cooperatively arranged J-pins 91 projecting radially inwardly from the overshot whenever the overshot is lowered over the fishing neck. After the I-pins 91 enter the slots 90, the pins are lockingly engaged in the closed short portion of the slots by a concerted application of left-hand torque and a slight upward pull on the tubing 11. Conversely, the overshot 15 is selectively disengaged from the fishing neck 16 by lowering the tubing 11 slightly, torquing the tubing to the right, and then pulling upwardly.

The fishing neck 16 closes off the upper end of the longitudinal bore 86 extending through the index mandrel 21. A group of lateral equalizing ports 92 are provided around the upper end of the mandrel 21 immediately below the fishing neck 16. Fluid communication through these ports 92 is selectively controlled by an annular valve member 93 which is slidably disposed around the mandrel 21 immediately below the equalizing ports. O-rings 94-97 around the inner surface of the valve member 93 and outer surface of the mandrel 21 fluidly seal the ports 92 whenever the equalizing valve member 93 is shifted upwardly to its closed position.

This slidable valve member 93 is cooperatively arranged to be longitudinally shifted by particular manipulation of the running overshot 15 so that the equalizing ports 92 are uncovered whenever the overshot is engaged over the fishing neck 16 and covered whenever the overshot is removed. A shoulder 98 projecting inwardly from the central portion of the overshot 15 is arranged to engage the upper end of sliding valve member 93 and shift the valve member downwardly to its open position as the overshot is being coupled onto the fishing neck 16. Whenever the overshot 15 is removed by torquing it to the right and picking up, a group of resilient fingers 99 spaced around the lower portion of the overshot are provided with inwardly projected shoulders 100 arranged to engage a shoulder 101 on the sliding valve member 93 and pull it upwardly to close the equalizing ports 92. Depending resilient fingers 102 around the lower end of the slidable valve member 93 are cooperatively arranged to be cammed outwardly as they pass over an annular shoulder 103 around the index mandrel 21 and then retracted after clearing the shoulder. Thus, the lower ends 104 of these fingers 102 will engage the upwardly facing portion of the annular shoulder 103 and hold the slidable valve member 93 in its uppermost or port-closing position after the overshot 15 has been removed.

Accordingly, whenever the mandrel 21 has been rotated sufficiently to set the packing means 20 into sealing engagement with the casing, the overshot 15 will then be disengaged from the fishing neck 16 and moved on up the well bore. As already explained, removal of the overshot 15 shifts the slidable valve member 93 upwardly and closes the equalizing ports 92 to completely block fluid communication from one side of the bridge plug 14 to the other.

Whenever it is desired to release and retrieve the bridge plug 14, the overshot 15 is dropped over and re-engaged with the fishing neck 16. Once the overshot 15 reaches its engaging position, J-pins 91 will re-enter the upper end of the J-slots 90 on the fishing neck 16. As the J-pins 91 re-enter the closed portion of the slots 90, the slidable valve member 93 is again shifted downwardly to re-open the equalizing ports 92. Thus, pressure will be equalized across the bridge plug 14 which will enable it to be retracted and easily removed.

Retraction of the bridge plug 14 is simply done by rotating the mandrel 21 to the left, which action returns the tubular sleeve member 18 upwardly along the threads 25 in the housing 19, thereby relaxing the packing means 20 and allowing it to reassume its normal configuration.

It will also be appreciated that whenever the tubular sleeve 18 has been screwed back upwardly to its initial starting position, the mandrel 21 should be in a position relative to the housing 19 that the locking lug end 36 is again substantially realigned with the T-groove 37 in the outer surface of the mandrel. If the lug 33 does not relatch, however, the operator needs only to shift the tubing 11 and mandrel 21 upwardly and downwardly slightly until the lug end 36 re-enters the divergent portion 39 of the T-groove 37. The operator cannot observe the operation of this lug, of course, but inasmuch as the anchor 24 will remain engaged with the casing so long as the mandrel 21 is not locked, the bridge plug 14 cannot be moved until the lug end 36 has re-entered the elongated portion 38 of the T-groove 37.

As an added feature, it will be noted in FIG. 2C that should annular spacer member 79 be reversed end-for-end, the compensating piston 75 will be shifted upwardly a substantial distance. It will be understood, of course, that such reversal will accordingly displace more fluid into the hydraulic system proper, which will naturally inflate the elastomeric sleeve 47 a corresponding amount. Accordingly, by properly proportioning the dimensions of the hydraulic system, one particular model of the bridge plug 14 may be successfully operated in various sizes of casing having widely differing internal diameters. By pre-inflating the elastomeric sleeve 47 in this manner, the casingengaging members 48, 49 will consequently be moved closer to the casing before the mandrel 21 is actuated. Thus, it is made certain that the members 48 and 49 will engage the casing before the mandrel 21 has been shifted its full extent thereby ensuring that additional longitudinal shifting of the mandrel will serve to press the members more tightly against the casing.

It will be appreciated that compression spring 78 (FIG. 2C) can be made sufiiciently strong that it will urge the compensating piston 75 upwardly with sufiicient force to develop a slight pressure in the hydraulic system. Accordingly, by selecting a suitable spring 75 and eliminating the arcuate springs 57 on opposite ends of the casing-engaging members 48 and 49, the elastomeric sleeve 47 will be expanded outwardly at all times. Thus, by developing a slight hydraulic pressure in the system in this manner, the casing-engaging members 48 and 49 will anchor the housing 19 sufficiently to eliminate the need for drag blocks 23.

Turning now to FIGS. 5A and 5B, another embodiment is shown of a retrievable bridge plug employing the principles of the present invention. The retrievable bridge plug 100 depicted in FIGS. 5A and 5B is similar in many respects to that already described and includes a movable body member or mandrel 101 telescopically arranged within a tubular housing 102. Oppositely directed elastomeric packing cups 103 and 104 are mounted around the upper end of the housing 102 and separated from one another by elastomeric back-up rings 105 and 106. Thus, whenever there is a pressure differential across the cups 103 and 104, one or the other of them will be expanded outwardly into sealing engagement with the casing.

For establishing the longitudinal position of the mandrel 101 relative to the housing 102, an outwardly projecting lug 107 on the central portion of the mandrel is slidably received within a generally T -shaped slot system 108 formed in the adjacent internal housing wall. The slot system 108 is comprised of an elongated longitudinal slot 109 that is parallel to a shorter slot 110 and interconnected at their centers by a circumferential slot portion 111. Thus, so long as the lug 107 is confined within the shorter slot portion 110, the mandrel 101 cannot shift appreciably in either longitudinal direction relative to the housing 102 and, therefore, is less susceptible to inadvertent release as it is being positioned in a well bore. The mandrel 101, therefore, must first be torqued to the right to move the lug 107 through the connecting slot 111 into the longer longitudinal slot 109. Once the lug 107 is shifted into the longer slot 109, the mandrel 101 is, of course, free to shift longitudinally an appreciable distance relative to the housing 102.

A hydraulically actuated, radially expansible friction anchor 112 is arranged and mounted around the central portion of the housing 102 in the same manner as that previously described and illustrated in FIGS. 2 and 4. An axial bore 113 extending the full length of the mandrel 101 is capped at its upper end by a fishing neck 114 arranged to cooperatively receive an overshot (not shown) as also previously described. A slidable valve member 115 is operatively arranged around the upper end of the mandrel 101 in the same manner as that shown in FIG. 2A to selectively close a plurality of equalizing ports 116 whenever the overshot is removed.

It will be appreciated that when the usual bridge plug of the type illustrated is being shifted downwardly in a fluid-filled well bore, a pressure differential may develop between fluids trapped in the annular space between the packing cups and the well fluids surrounding the tool above and below the packing cups. Such pressure differential tends to expand the cups into sealing engagement with the casing wall, resulting in a swabbing action which can damage the packing cups and deleteriously affect the speed at which the bridge plug can be lowered into the well.

To eliminate this swabbing action, means are provided in bridge plug 100 for equalizing the fluid pressure between the cups 103 and 104 with that of the fluids above and below the cups so long as the mandrel lug 107 is confined within the shorter slot portion 110. To accomplish this, as seen in greater detail in FIG. 6, an inwardly biased valve member 117 having an axial passage 118 is slidably disposed in a hollowed valve body 119 that is closed at its .outer end and fluidly sealed within a lateral bore 120 through the housing 102 between the cups 103 and 104. When the valve member 117 is in one position, O-rings 121 and 122 around the valve member are arranged to be spaced inwardly and outwardly of a port 123 through the valve body 119 and opening to the exterior of the housing 102 between the cups 103 and 104.

A flat surface 124 formed across the mandrel 101 is so aligned that whenever the mandrel lug 107 is confined within the shorter housing slot 110, the inner end 125 of the valve member 117 is engaged with the mandrel flat. With the valve member 117 in this position, the valve member and O-ring 122 are displaced inwardly from the port 123 to admit fluids in the well through a lateral housing passage 126 below the packing cups 103 and 104 into the clearance space 127 between the mandrel 101 and housing 102 to equalize the pressure between the cups. Then, whenever the mandrel 101 is manipulated to bring the mandrel lug 107 into the elongated slot 109, the inner end 125 of the valve member 117 will be cammed .outwardly by the peripheral surface of the mandrel adjacent to the flat 124. Thus, once the mandrel 101 has been rotated to bring the lug 107 into the elongated slot 109, the valve member 117 will be shifted to its outermost position and sealed by O-rings 121 and 122 to block fluid communication between port 123 and axial passage 118.

Turning now to the hydraulic system of the friction anchor 112, the housing 102 is formed in such a manner as to provide an annular chamber 128 (FIG. A) above the upper end of the anchor. A similar annular chamber 129 (FIG. 5B) is also formed below the lower end of the anchor 112. The annular clearance space 130 between the mandrel 101 and housing 102 at this point provides fluid communication between the upper chamber 128 and lower chamber 129. A plurality of radial ports 131 through the housing 102 adjacent the elastomeric sleeve 132 provide fluid communication from this clearance 130 into the sealed space 133 underneath the elastomeric sleeve.

The upper end of the upper annular chamber 128 and lower end of the lower annular chamber 129 are respectively closed by annular piston members 134 and 135 which are slidably mounted therein and fluidly sealed by O-rings 136-139 to both the housing 102 and the mandrel 101. The upper slidable piston member 134 is free to move downwardly in the upper chamber 128 until reaching an upwardly directed housing shoulder 140 therein. The lower slidable piston member 135 is normally biased downwardly by a spring 141 against an upwardly directed shoulder 142 formed in the housing 102 at the lower end of the lower chamber 129.

A mandrel shoulder 143 a short distance above the upper slidable piston 134 is suitably arranged to engage the upper piston and force it downwardly whenever the mandrel 101 shifts downwardly. Similarly, a second mandrel shoulder 144 is arranged below the piston 135 to engage and shift the lower piston member upwardly whenever the mandrel 101 shifts in that direction.

It will be appreciated, therefore, that with a suitable fluid in the above described hydraulic system, longitudinal shifting of the mandrel 101 in either direction will expand the elastomeric sleeve 132 of the anchor 112 and press the casing-engaging members 145 and 146 against the casing. A compensating chamber 147 is formed in the housing 102 beneath the lower piston member 135 to maintain a supply of fluid in the hydraulic system as well as to compensate for thermal expansion of the fluid. The lower end of this compensating chamber 147 is closed by a slidable annular compensating piston member 148 having O-rings 149 and 150 around its inner and outer surfaces to fluidly seal the compensating piston relative to the housing 102 and the mandrel 101.

For reasons that will subsequently become apparent, a sleeve 151 is slidably disposed in the lower end of the housing 102 and releasably secured thereto by a frangible shear pin 152 or the like to hold the upper end 153 of the sleeve a short distance below the compensating piston 148. A compression spring 154 is mounted around the sleeve 151 and confined between an upwardly directed housing shoulder 155 and the upper sleeve end 153. An annular piston member 156 having a reduced-diameter upper portion 157 and an enlarged-diameter lower portion 158 is slidably disposed within the housing 102 below the shear pin 152. O-rings 159 and 160, respectively, around the enlarged and reduced portions 158 and 157 of the piston 156 are spaced from one another and fluidly seal the piston relative to the housing 102 to define an enclosed, sealed space 161 therebetween.

Selectively controlled fluid communication is provided between the compensating chamber 147 and the remainder of the hydraulic system through a housing passage 162 and an annular clearance space formed by "a reduced diameter portion 163 around the mandrel 101. This reduced-diameter portion 163 is arranged to be in juxtaposition with the lower piston 135 whenever the mandrel 101 is in its intermediate position as determined by the mandrel lug 107 being confined within the shorter slot 110. When, however, the mandrel 101 is so manipulated to shift the lug 107 into the longer slot 109 and the mandrel is shifted longitudinally only a slight distance in either direction, the inner O'-ring 138 within the lower piston member 135 fluidly seals the piston to the mandrel at either 164 or 165, depending upon the direction in which the mandrel has been shifted.

Accordingly, it will be seen that so long as the mandrel -101 is in a neutral or inter-mediate position (as determined by the lug 107 being within the short slot 110), the mandrel is substantially restrained from shifting longitudinally in either direction. Thus, so long as the mandrel 101 is in this intermediate position, the upper and lower piston members 134 and 135 will be substantially in the positions illustrated in FIG. 5 and the mandrel shoulders 143 and 144 will be separated therefrom. With the mandrel 101 in this intermediate position, there will also be fluid communication between the compensating chamber 147 by way of the reduced-diameter mandrel portion 163 to permit free communication of the hydraulic fluid from the compensating chamber into the remainder of the hydraulic system.

Turning now to the operation of the bridge plug 100, it will be realized that to shift the mandrel lug 107 within the slot system 108, means must be provided to hold the housing 102 fixed relative to the mandrel 101. Moreover, after the bridge plug 100 has been set, the housing 102 must remain anchored to the casing with a minimum holding force either when the mandrel 101 is not sutficiently displaced to shift one of the pistons 134 and 135 or as it is shifting through its intermediate position to one of the other positions. It will be recognized, of course, that were the lower spring 154 always engaged with the compensating piston 148-, the compensating piston would be urged upwardly to develop a pressure in the hydraulic system that was proportionately related to the spring force. Thus, by selecting a suitable spring rate for the spring 154, a predetermined hydraulic pressure would be developed to maintain the wall-engaging members 145 and 146 engaged against the casing with a holding force that is adequate to accomplish the above-described functions.

Although this approach is successful in some operations, it has been found difficult in other instances to shift a bridge plug arranged in this manner downwardly in the well bore before it has reached a depth where the tubing string has suflficient weight to overcome the abovementioned holding force. Inasmuch as the minium holding force may well be in the order of a few thousands of pounds, it will be recognized that, in some instances, several hundreds of feet of tubing will be required before the weight of the assembled tubing string will freely shift the bridge plug downwardly.

Accordingly, in the bridge plug 100 depicted in FIGS. A and 5B, means are provided for initially removing the spring bias from the compensating piston 148 until such time that the bridge plug has reached a predetermined depth in a well bore. To accomplish this, the retainer sleeve 51 is secured at its lower end to the housing 102 by the shear pin 152 to depress the spring 154 below the compensating piston 148. By spacing the retainer sleeve 151 below the compensating piston 148, the compensating piston is free to move downwardly to accommodate thermal expansion of the hydraulic fluid within the system as the bridge plug 100 is lowered into Warmer environments.

To release the retainer sleeve 151, the stepped piston 156 immediately below the shear pin 152 is appropriately arranged to move upwardly and into engagement with the lower end of the retainer sleeve in response to the hydrostatic pressure of fluids in the well bore. It will be appreciated that as the bridge plug 100 is assembled at the surface, the space 161 between O-rings 159 and 160 will be at atmospheric pressure. Thus, as the hydrostatic pressure increases during the descent of the bridge plug 100, it will act upon the effective cross-sectional area between O-rings 159 and 160 to urge the piston member 156 upwardly against the lower end of the retainer sleeve 151 with a force proportionately related to the hydrostatic pressure. Then, whenever the bridge plug 100 has reached a depth at which the hydrostatic pressure is sufficient to enable the piston 156 to shear the pin 152, the retainer sleeve 151 will be released from the housing 102 and be carried upwardly by the compensating spring 154 until its upper end 153 engages the compensating piston 148 immediately below the O-ring 150. Once the compensating spring 154 has been released, it will be appreciated that it will urge the compensating piston 148 upwardly with a predetermined force calculated to develop suflicient hydraulic pressure within the system to move the casing-engaging members 145 and 146 outwardly against the casing with a desired holding force.

Once the bridge plug has been positioned at the depth at which it is to be set, it is halted and the overshot (not shown) removed as previously described. As the overshot is removed, the mandrel 101 is shifted upwardly relative to the housing 102 to first sealingly engage the O-ring 138 within the lower piston at 164 on the mandrel and, thereafter, bring lower mandrel shoulder 144 against the lower piston and shift it upwardly. As the lower piston 135 is shifted upwardly, it will be appreciated that a hydraulic pressure will be developed within the hydraulic system to expand the casing-engaging members and 146 against the casing with still greater force. Thus, it will be appreciated that the bridge plug 100 will function similarly to that previously described.

Accordingly, it will be appreciated that the present invention provides a positive control for a hydraulically actuated anchor for a well tool. Where such a tool is a retrievable bridge plug, the cooperative arrangement disclosed herein will allow the bridge plug to be positioned within a well bore and then selectively actuated to set the bridge plug into sealing engagement with the casing. The arrangement allows the bridge plug to be anchored against the casing with a force proportional to the pressure differential across it. The arrangement further maintains the hydraulic system at any desired pressure regardless of ambient conditions within the well.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. In a well packer sized and adapted for reception in a well bore including a housing having a longitudinal bore, packing means operatively mounted on said housing and adapted for expansion into sealing engagement with a well bore, and actuator means movable relative to said housing for expanding said packing means to pack-off a well bore, the combination with said well packer of: anchoring means for securing said well packer relative to the well bore including outwardly-extendible wallengaging means mounted on said housing and fluidly sealed relative thereto to provide a fluid-tight space therebetween, said wall-engaging means being adapted for extension into engagement with the well bore upon application of hydraulic pressure in said fluid-tight space; first hydraulic means responsive to fluid pressure in a well bore for pressing said wall-engaging means into anchoring engagement with a force proportionately related to this pressure to anchor said well packer including a body member slidably disposed within said housing bore and arranged to shift longitudinally therein in response to fluid pressure in the well bore, a first piston member slidably disposed in said housing bore and adapted to be engaged by said body member and advancd along said bore thereby whenever said body member shifts in one direction, first means fluidly sealing said housing bore at a point longitudinally spaced from said first piston member in said one direction, second means fluidly sealing said first piston member for providing a first fluid-tight chamber in said housing bore intermediate said first piston member and said longitudinally displaced point, and conduit means providing fluid communication between said first fluid-tight chamber and said fluid-tight space; releasable latching means securing said body member against longitudinal shifting, said latching means being responsive to operation of said actuator means for expanding said packing means to free said body member for longitudinal shifting; and second hydraulic means for pressing said wall-engaging means into engagement to secure said housing from movement relative to said actuator means including a second piston member slidably disposed in said housing bore and separated from said first piston member by said first sealing means, third means fluidly sealing said second piston member for providing a second fluid-tight chamber in said housing bore intermediate said first sealing means and second piston member, said fluid-tight chambers and space being filled with fluid, biasing means normally urging said second piston member toward said first sealing means, passage means providing fluid communication between said fluid-tight chambers, and means responsive to shifting of said body member for selectively closing said fluid passage means whenever said body member shifts in said one direction.

2. In a well packer sized and adapted for reception in a well bore including a housing having a longitudinal bore, packing means operatively mounted on said housing and adapted for expansion into sealing engagement with the well bore, and actuator means movable relative to said housing for expanding said packing means to packoff a well bore, the combination with said well packer of: anchoring means for securing said well packer relative to the well bore including outwardly-extendible wallengaging means mounted on said housing and fluidly sealed relative thereto to provide a fluid-tight space therebetween, said Wall-engaging means being adapted for extension iuto engagement with the well bore upon application of hydraulic pressure in said fluid-tight space; first hydraulic means selectively responsive to fluid pressure in a well bore for pressing said wall-engaging means into anchoring engagment with a force proportionately related to this pressure to anchor said well packer including a body member slidably disposed within said housing bore and arranged to shift longitudinally therein in response to fluid pressure in the well bore, first and second piston members slidably disposed in said housing bore and spaced apart, first means fluidly sealing said piston members providing a first fluid-tight chamber in said housing bore between said first and second piston members, conduit means providing fluid communication between said first fluid-tight chamber and said fluid-tight space, first means for advancing said first piston member toward said second piston member whenever said body member shifts in one direction and second means for advancing said second piston member toward said first piston member whenever said body member shifts in the opposite direction; releasable latching means securing said body member against longitudinal shifting, said latching means being responsive to operation of said actuator means for expanding said packing means to free said body member for longitudinal shifting; and second hydraulic means for pressing said Wall-engaging means into engagement to secure said housing from movement relative to said actuator means including a third piston member slidably disposed in said housing bore and separated from said first piston member by said second piston member, second means fluidly sealing said third piston member for providing a second fluid-tight chamber in said housing bore intermediate said second and third piston members, said fluid-tight chambers'and space being filled with fluid, biasing means normally urging said third piston member toward said second piston member, passage means providing fluid communication between said fluid-tight chambers, and means responsive to shifting of said body member for selectively closing said fluid passage means whenever said body member shifts in either of said directions.

3. In a well packer sized and adapted for reception in a well bore including a housing having a longitudinal bore, packing means operatively mounted on said housing and adapted for expansion into sealing engagement with the well bore, and actuator means movable relative to said housing for expanding said packing means to packolf a well bore, the combination with said well packer of: anchoring means for securing said well packer relative to the well bore including outwardly-extendible wallengaging means mounted on said housing and fluidly sealed relative thereto to provide a fluid-tight space therebetween, said wall-engaging means being adapted for extension into engagement with the well bore upon application of hydraulic pressure in said fluid-tight space; first hydraulic means selectively responsive to fluid pressure in a well bore for pressing said wall-engaging means into anchoring engagement with a force proportionately related to this pressure to anchor said well packer including a body member slidably disposed within said housing bore and arranged to shift longitudinally therein in response to fluid pressure in the well bore, first and second annular piston members slidably disposed around said body member and slidably received within said housing bore, said annular piston members being spaced apart, first means fluidly sealing said annular piston members providing a first fluid-tight chamber in said housing bore between said annular piston members, conduit means providing fluid communication between said first fluid-tight chamber and said fluid-tight space, stop means limiting retrogression of said annular piston members, biasing means normally urging said annular piston members against said stop means, first means on said body member for advancing said first piston member toward said second piston member whenever said body member shifts in one direction and second means on said body member for advancing said second piston member toward said first piston member whenever said body member shifts in the opposite direction; releasable latching means securing said body member against longitudinal shifting, said latching means being responsve to operation of said actuator means for expanding said packing means to free said body member for longitudinal shifting; and second hydraulic means for pressing said wall-engaging means into engagement to secure said housing from movement relative to said actuator means including a third piston member slidably disposed in said housing bore and separated from said first piston member by said second piston member, second means fluidly sealing said third piston member for providing a second fluid-tight chamber in said housing bore intermediate said second and third piston members, said fluid-tight chambers and space being filled with fluid, biasing means normally urging said third piston member toward said second piston member, passage means on said body member normally in juxtaposition with said second piston member providing fluid communication between said fluid-tight chambers, and third means responsive to shifting of said body member fluidly sealing said body member to said second piston member for selectively closing said fluid passage means whenever said body member shifts in either of said directions.

4. A well packer sized and adapted for reception in a well bore for packing-off the well bore, comprising: a housing having a central longitudinal bore; a rotatable tubular member threadedly engaged with said housing, said tubular member having a fixed shoulder longitudinally spaced from said housing; packing means mounted around said tubular member intermediate said shoulder and said housing, said packing means being adapted for expansion into sealing engagement with the well bore upon rotation of said tubular member; anchoring means for securing said well packer relative to the well bore including an inflatable elastomeric sleeve sealingly mounted around said housing to provide a fluid-tight space there between and wall-engaging means mounted around said elastomeric sleeve, said'elastomeric sleeve being adapted to inflate upon application of hydraulic pressure in said fluid-tight space to pres-s said wall-engaging means into engagement with the well bore; a rotatable body member slidably disposed within said tubular member and housing bore and arranged to shift therein in response to fluid pressure in a well bore; releasable latching means securing said body member against longitudinal shifting, said latching means being responsive to rotation of said body member for expanding said packing means to free said body member for longitudinal shifting; first hydraulic means for inflating said elastomeric sleeve to press said wall-engaging means into engagement with the well bore with sufficient force to secure said housing against rotation relative to said body member including first means fluidly sealing-off a portion of said housing bore, a piston member slidably disposed in said housing bore and longitudinally displaced from said first sealing means, biasing means normally urging said piston member toward said first sealing means, second means fluidly sealing said piston member providing a fluid-tight chamber in said housing bore intermediate said first sealing means and piston member, and conduit means providing fluid communication between said fluid-tight chamber and said fluid-tight space, said fluid-tight chamber and space being filled with fluid; and second hydraulic means for inflating said elastomeric sleeve to press said wall-engaging means into anchoring engagement with the well bore with a force proportionately related to fluid pressure in the well bore including an annular piston member slidably disposed around said body member and slidably received in said housing bore within said fluid-tight chamber, third means fluidly sealing said annular piston relative to said housing, fluid passage means on said body member normally in juxtaposition with said annular piston providing fluid communication across said annular piston whenever said body member is secured by said latching means, fourth means adapted to fluidly seal said fluid passage means whenever said body member is shifted for blocking fluid communication across said annular piston, and means on said body member adapted to engage and advance said annular piston member whenever said body member is shifted toward said first sealing means to develop a hydraulic pressure in said fluid-filled space.

5. A well packer sized and adapted for reception in a well bore for packing-oil the well bore, comprising: an outer tubular member; a body member slidably disposed within the bore of said outer member and operatively arranged to be shifted longitudinally from a first position relative thereto to another position in response to a differential of fluid pressure above and below said members in a well bore; packing means operatively mounted on one of said members and arranged for expansion into sealing engagement with the well bore; anchoring means for securing said packer against movement relative to the well bore including outwardly-extendible wall-engaging means mounted on said outer member and fluidly sealed relative thereto to provide a fluid-tight space therebetween, said wall-engaging means being adapted for extension into engagement with the well bore upon application of hydraulic pressure in said fluid-tight space; first hydraulic means responsive to shifting of said body member from said first position for applying a hydraulic pressure in said fluid-tight space to press said wall-engaging means into anchoring engagement with a force proportionately related to said pressure differential including first and second piston members slidably disposed in said tubular member bore and spaced apart, first and second means respectively fluidly sealing said piston members for providing a first fluid-tight chamber in said tubular member bore between said first and second piston members, first passage means providing fluid communication between said first fluid-tight chamber and said fluid-tight space, first means for advancing said first piston member toward said second piston member whenever said body member shifts in one direction and second means for advancing said second piston member toward said first piston member whenever said body member shifts in the opposite direction; second hydraulic means for applying a hydraulic pressure in said fluid-tight space to maintain said wall-engaging means engaged with the well bore when said body member is in said first position including a third piston member slidably disposed in said tubular member bore and longitudinally displaced from said other piston members, third means fluidly sealing said third piston member for providing a second fluid-tight chamber in said tubular member bore between said third piston member and one of said other piston members, second passage means providing fluid communication between said chambers, said passage means, fluid-tight chambers and fluidtight space being filled with fluid and means biasing said third piston member toward said other piston members; and means responsive to shifting of said body member from said first position for fluidly sealing said second passage means.

6. A well packer sized and adapted for reception in a well bore for packing-off the well bore, comprising: an outer tubular member; a body member slidably disposed Within the bore of said outer member and operatively arranged to be shifted longitudinally from a first position relative thereto to another position in response to a differential of fluid pressure above and below said members in a well bore; packing means operatively mounted on one of said members and arranged for expansion into sealing engagement with the well bore; anchoring means for securing said packer against movement relative to the well bore including outwardlyextendible wall-engaging means mounted on said outer member and fluidly sealed relative thereto to provide a fluid-tight space therebetween, said wall-engaging means being adapted for extension into engagement with the well bore upon application of hydraulic pressure in said fluid-tight space; first hydraulic means responsive to shifting of said body member from said first position for applying a hydraulic pressure in said fluid-tight space to press said wall-engaging means into anchoring engagement with a force proportionately related to said pressure differential including first and second annular piston members slidably disposed around said body member and slidably received within said tubular member bore, said piston members being spaced apart, first and second means respectively fluidly sealing said piston members for providing a first fluid-tight chamber in said tubular member bore between said first and second piston members, first passage means providing fluid communication between said first fiuid-tight chamber and said fluid-tight space, stop means limiting retrogression of said first and second piston members, first means on said body member for advancing said first piston member toward said second piston member whenever said body member shifts in one direction and second means on said body member for advancing said second piston member toward said first piston member whenever said body member shifts in the opposite direction; second hydraulic means for applying a hydraulic pressure in said fluid-tight space to maintain said wall-engaging means engaged with the well bore when said body member is in said first position including a third piston member slidably disposed in said tubular member bore and longitudinally displaced from said other piston members, third means fluidly sealing said third piston member for providing a second fluid-tight chamber in said tubular member bore between said third piston member and one of said other piston members, second passage means providing fluid communication between said chambers, said passage means, fluid-tight chambers and fluid-tight space being filled with fluid and means biasing said third piston member toward said other piston members; and means responsive to shifting of said body member from said first position for fluidly sealing said second passage means.

7. A well packer sized and adapted for reception in a well bore for packing-off the well bore comprising: an outer tubular member; a body member slidably disposed within the bore of said outer member and operatively arranged to be shifted longitudinally from a first position relative thereto to another position in response to a differential of fluid pressure above and below said 17 members in a well bore; packing means operatively mounted on one of said members and arranged for expansion into sealing engagement with the well bore; anchoring means for securing said packer against movement relative to the well bore including outwardlyextendible wall-engaging means mounted on said outer member and fluidly sealed relative thereto to provide a fluid-tight space therebetween, said wall-engaging means being adapted for extension into engagement with the well bore upon application of hydraulic pressure in said fluid-tight space; first hydraulic means responsive to shifting of said body member from said first position for applying a hydraulic pressure in said fluid-tight space to press said wall-engaging means into anchoring engagement with a force proportionately related to said pressure differential including first and second annular piston members slidably disposed around said body member and slidably received within said tubular member bore, said piston members being spaced apart, first and second means respectively fluidly sealing said piston members for providing 'a first fluid-tight chamber in said tubular member bore between said first and second piston members, first passage means providing fluid communication between said first fluid-tight chamber and said fluid-tight space, stop means limiting retrogression of said first and second piston members, first means on said body member for advancing said first piston member toward said second piston member whenever said body member shifts in one direction and second means on said body member for advancing said second piston member toward said first piston member whenever said body member shifts in the opposite direction; second hydraulic means for applying a hydraulic pressure in said fluid-tight space to maintain said wall-engaging means engaged with thewell bore when said body member is in said first position including a third piston member slidably disposed in said tubular member bore and longitudinally displaced from said other piston members, third means fluidly sealing said third piston member for providing a second fluid-tight chamber in said tubular member bore between said third piston member and one of said other piston members, second passage means in said body member and normally in juxtaposition with said one annular piston member for providing fluid communication across said one annular piston member between said chambers, said passage means, fluid-tight chambers and fluid-tight space being filled with fluid and means biasing said third piston member toward said other piston members; and means responsive toshifting of said body member from said first position for fluidly sealing said second passage means including fourth means fluidly sealing said one annular piston member to said body member whenever said second passage means has been shifted out of juxtaposition with said one annular piston member.

8. A well tool sized and adapted for reception in a well bore comprising: a housing; anchoring means for securing said well tool to the well bore operatively mounted on said housing and arranged for extension into engagement with the well bore in response to application of hydraulic pressure thereto; a body member operatively engaged with said housing and arranged to shift relative thereto in response to application of a force thereon; first hydraulic means in fluid communication with said anchoring means and responsive to the pressure of fluids in the well bore for applying hydraulic pressure to said anchoring means to secure said housing for movement relative to said body member; second hydraulic means in fluid communication with said anchoring means and responsive to shifting of said body member for applying hydraulic pressure to said anchoring means to anchor said well tool with a force proportionately related to the distance said body member is shifted; and means responsive to the shifting of said body member for closing-off fluid communication between said first hydraulic means and said anchor means.

9. A well tool sized and adapted for reception in a well bore comprising: a housing having a longitudinal bore; anchoring means for securing said well tool to the well bore including wall-engaging means operatively mounted on said housing to provide a fluid-tight space therebetween and arranged for extension into engagement with the well bore in response to application of hydraulic pressure in said fluid-tight space; a body member slidably disposed in said housing bore and operatively arranged to shift therein in response to application of a force thereon; first hydraulic means for applying hydraulic pressure to said fluid-tight space to press said wall-engaging means into engagement and secure said housing from movement relative to said body member including a first piston member slidably disposed in said housing bore, means normally urging said first piston member in one direction, first means fluidly sealing said first piston member relative to said housing, second means fluidly sealing said housing bore at a point longitudinally spaced in said one direction from said first piston member providing a first fluid-tight chamber in said housing bore intermediate said first piston member and said longitudinally displaced point, and conduit means providing fluid communication between said first fluid-tight chamber and said fluid-tight space; second hydraulic means responsive to shifting of said body member for applying hydraulic pressure to said fluid-tight space to press said wall-engaging means into engagement and anchor said well tool with a force proportionately related to the distance said body member is shifted including a second piston member slidably disposed in said housing bore at a point longitudinally spaced in said one direction from said second sealing means, said second piston member being operatively arranged and adapted to be engaged by said body member and advanced along said housing bore thereby whenever said body member shifts in the opposite direction, third means fluidly sealing said second piston member for providing a second fluid-tight chamber in said housing bore intermediate said second sealing means and second piston member, said fluid-tight chambers and space being filled with fluid, passage means providing fluid communication between said fluid-tight chambers; and means responsive to shifting of said body member for selectively closing said fluid passage whenever said body member shifts in said opposite direction.

10. A well tool sized and adapted for reception in a well bore comprising: a housing having a longitudinal bore; anchoring means for securing said well tool to the well bore including wall-engaging means operatively mounted on said housing to provide a fluid-tight space therebetween and arranged for extension into engagement with the well bore in response to application of hydraulic pressure in said fluid-tight space; a body member slidably disposed in said housing bore and operatively arranged to shift therein in response to application of a force thereon; first hydraulic means for applying hydraulic pressure to said fluid-tight space to press said wall-engaging means into engagement and secure said housing from movement relative to said body member including a first piston member slidably disposed in said housing bore, means normally urging said first piston member in one direction and first means fluidly sealing said first piston member relative to said housing; second hydraulic means responsive to shifting of said body member for applying hydraulic pressure to said fluid-tight space to press said wallengaging means into engagement and anchor said well tool with a force proportionately related to the distance said body member is shifted including second and third piston members spaced apart from one another and slidably disposed in said housing bore at points longitudinally spaced in said one direction from said first piston member, first means on said body member for advancing said second piston member toward said third piston member whenever said body member shifts in one direction, second means on said body member for advancing said third piston member toward said second piston member whenever said body member shifts in the opposite direction, second and third means fluidly sealing said second and third piston members relative to said housing providing first and second fluid-tight chambers in said housing bore intermediate said first and third piston members on either side of said second piston member and conduit means providing fluid communication between one of said fluidtight chambers and said fluid-tight space, said fluid-tight chambers and space being filled with fluid; passage means normally providing fluid communication between said fluid-tight chambers; and means responsive to shifting of said body member for selectively closing said fluid passage whenever said body member shifts in either of said directions.

11. A retrievable bridge plug sized and adapted for reception in a well bore comprising: telescoping inner and outer members, said members being relatively movable between upper, lower and intermediate locations, said members having a space therebetween and sealing means between said members, pack-off means on one of said members, hydraulically actuatable wall-engaging means on said outer member and having fluid communication to said space, upper and lower slidable piston means in said space, a fluid in said space whereby said piston means may apply pressure to said wall-engaging means, means on one of said members selectively cooperating with one or the other of said pistons in said upper and lower locations to apply pressure; means for releasably holding said members in said intermediate location, passage means through said inner member, valve means for selectively closing said passage, a closed chamber containing fluid, piston means in said chamber, spring means for acting on said last-mentioned piston means for applying pressure to the fluid in said closed chamber, and bypass means operative only in said intermediate location for placing said closed chamber in fluid communication with said space.

12. A packer for use in a well conduit comprising: inner and outer telescoping members, oppositely facing cup packers on said outer member, segmented, expandable elements mounted on said outer member and having outer surfaces for frictionally engaging a well conduit, an expandable fluid-tight sleeve on said body adjacent said elements for expanding said elements into engagement with a well conduit, said members having a space therebetween in fluid communication with said sleeve, upper and lower slidable piston means in said space and defining a closed chamber, a fluid in said closed chamber, means for limiting motion of said pistons in a direction away from one another, upper and lower shoulder means on said inner member for respectively engaging said piston means for moving a piston to apply pressure to said sleeve and actuate said elements, means on said inner member for bypassing fluid around one of said pistons, a pressure chamber in said outer member in fluid communication with said bypass means, piston means in said pressure chamber, and spring means for actuating said last-mentioned piston means to apply pressure to said sleeve.

13. A packer for use in a well conduit comprising: inner and outer telescoping members, pack-off means on said outer member, expandable elements mounted on said outer member and having outer surfaces for engaging a well conduit, an expandable fluid-tight sleeve on said body adjacent said elements for expanding said elements into engagement with a well conduit, said members having a space therebetween in fluid communication with said sleeve, upper and lower slidable piston means in said space and defining a closed chamber, a fluid in said closed chamber, means for limiting motion of said pistons in a direction away from one another, means on said inner member for respectively engaging said piston means for moving a piston to apply pressure to said sleeve and actuate said elements, means on said inner member for bypassing fluid around one of said pistons, a pressure chamber in said outer member in fluid communication with said bypass means, piston means in said pressure chamber, and spring means for actuating said last-mentioned piston means to apply pressure to said sleeve.

14. A packer for use in a well conduit comprising: inner and outer telescoping members, oppositely facing cup packers on said outer member, segmented, expandable elements mounted on said outer member and having outer surfaces for frictionally engaging a well conduit, an expandable fluid-tight sleeve in said body adjacent said elements for expanding said elements into engagement with a well conduit, said members having a space therebetween in fluid communication with said sleeve, upper and lower slidable piston means in said space above and below said sleeve and defining a closed chamber, a fluid in said closed chamber, means for limiting motion of said pistons in a direction away from said sleeve, said inner member being movable relative to said outer member between upper, lower and intermediate locations, upper and lower shoulder means on said inner member for respectively engaging said piston means in said upper and lower locations for moving a piston to apply pressure to said sleeve and actuate said elements, means on said inner member for bypassing fluid around one of said pistons when said inner member is in said intermediate location, a pressure chamber in said outer member in fluid communication with said bypass means, piston means in said pressure chamber, and spring means for actuating said last-mentioned piston means to apply pressure to said sleeve.

15. A packer for use in a well conduit comprising: inner and outer telescoping members, oppositely facing cup packers on said outer member, segmented, expandable elements mounted on said outer member and having outer surfaces for frictionally engaging a well conduit, an ex pandable fluid-tight sleeve in said body adjacent said elements for expanding said elements into engagement with a well conduit, said members having a space therebetween in fluid communication with said sleeve, upper and lower slidable piston means in said space above and below said sleeve and defining a closed chamber, a fluid in said closed chamber, means for limiting motion of said pistons in a direction away from said sleeve, said inner member being movable relative to said outer member between upper, lower and intermediate locations, upper and lower shoulder means on said inner member for respectively engaging said piston means in said upper and lower locations for moving a piston to apply pressure to said sleeve and actuate said elements, means on said inner member for bypassing fluid around one of said pistons when said inner member is in said intermediate location, a pressure chamber in said outer member in fluid communication with said bypass means, piston means in said pressure chamber, spring means for actuating said last-mentioned piston means to apply pressure to said sleeve, and means for releasably holding said members in said intermediate position.

16. A packer for use in a well conduit comprising: inner and outer telescoping members, said inner member having a passage therethrough, oppositely facing cup packers on said outer member, segmented, expandable elements mounted on said outer member and having outer surfaces for frictionally engaging a well conduit, an expandable fluid-tight sleeve in said body adjacent said elements for expanding said elements into engagement with a well conduit, said members having a space therebetween in fluid communication with said sleeve, upper and lower slidable piston means in said space above and below said sleeve and defining a closed chamber, a fluid in said closed chamber, means for limiting motion of said pistons in a direction away from said sleeve, said inner member being movable relative to said outer member between u per, lower and intermediate locations, upper and lower shoulder means on said inner member for respectively en-' aabepo 21 22 gaging said piston means in said upper and lower loca References Cited by the Examiner tions for moving a piston to apply pressure to said sleeve UNITED STATES PATENTS and actuate said elements, means on said inner member for bypassing fluid around one of said pistons when said 2,638,168 5/1953 Parks 166 120 inner member is in said'intermediate location, a pressure 5 29251128 2/1960 166-121 chamber in said outer member in fluid communication 2,990,883 7/1961 Lewls 166-212 X with said bypass means, piston means in said pressure 3,233,675 2/1266 Tamplen et a1 166-420 chamber, spring means for actuating said last-mentioned piston means to apply pressure to said sleeve, and means CHARLES O CQNNELL P'lmary Examiner for selectively closing said passage. 10 D. H. BROWN, Assistant Examiner. 

13. A PACKER FOR USE IN A WELL CONDUIT COMPRISING: INNER AND OUTER TELESCOPING MEMBERS, PACK-OFF MEANS ON SAID OUTER MEMBER, EXPANDABLE ELEMENTS MOUNTED ON SAID OUTER MEMBER AND HAVING OUTER SURFACES FOR ENGAGING A WELL CONDUIT, AN EXPANDABLE FLUID-TIGHT SLEEVE ON SAID BODY ADJACENT SAID ELEMENTS FOR EXPANDING SAID ELEMENTS INTO ENGAGEMENT WITH A WELL CONDUIT, SAID MEMBERS HAVING A SPACE THEREBETWEEN IN FLUID COMMUNICATION WITH SAID SLEEVE, UPPER AND LOWER SLIDABLE PISTON MEANS IN SAID SPACE AND DEFINING A CLOSED CHAMBER, A FLUID IN SAID CLOSED CHAMBER, MEANS FOR LIMITING MOTION OF SAID PISTONS IN A DIRECTION AWAY FROM ONE ANOTHER, MEANS ON SAID INNER MEMBER FOR RESPECTIVELY ENGAGING SAID PISTON MEANS FOR MOVING A PISTON TO APPLY PRESSURE TO SAID SLEEVE AND ACTUATE SAID ELEMENTS, MEANS ON SAID INNER MEMBER FOR BYPASSING FLUID AROUND ONE OF SAID PISTONS, A PRESSURE CHAMBER IN SAID OUTER MEMBER IN FLUID COMMUNICATION WITH SAID BYPASS MEANS, PISTON MEANS IN SAID PRESSURE CHAMBER, AND SPRING MEANS FOR ACTUATING SAID LAST-MENTIONED PISTON MEANS TO APPLY PRESSURE TO SAID SLEEVE. 